The present invention relates to an electronic component having an electrode conductor formed of a photosensitive conductive paste and a non-photosensitive conductive paste, which are formed on an element, and a method for manufacturing the electronic component, and more particularly to an electronic component comprising an electrode conductor that is suitable for a chip inductor, an LC filter, a dielectric filter, and a non-reciprocal circuit element (circulator, isolator), and a manufacturing method for manufacturing this electronic component.
A conductive pattern for an electronic component is required to be fine and highly reliable. For example, recently, the portable telephones have advanced for higher frequency, and a number of leadless parts that have excellent frequency characteristics have been employed. In particular, for the electrode portions, it is demanded that the fine patterns as precise as in units of micron are produced stably at high yield. At the same time, the strength to withstand severe environments including high temperatures, vibrations, and humidity is required with high reliability.
Regarding the pattern precision, in the package for a chip inductor, a ceramic substrate, a ceramic multi-layer substrate or a semiconductor, for example, it is already required that the pattern precision, the pitch size or the line-and-space of an electrode conductor may be as small as 30 xcexcm to 50 xcexcm or below, because the current requirements for smaller size and higher frequency can not be met with the sizes of 100 xcexcm to 150 xcexcm as conventionally employed.
The mounting pattern or the electrode of mounted portion is demanded to be stronger and more highly reliable, because of the miniaturization. Further, the recent lead free trend causes the soldering temperatures to be raised, and there is a requirement for the heat-resisting electrode to withstand the high temperatures.
To form an electrode or a conductor pattern on the surface, a thick film printing method using the conductive paste is generally used, because the vacuum deposition involves a smaller film thickness of conductor, and the lower productivity. Employing a screen and a squeeze, a silver paste is printed on a ceramic element to form a conductor pattern. Thereafter, a drying process is undergone, and the conductor pattern is sintered at a temperature from about 450xc2x0 C. to 1000xc2x0 C., whereby an electrode conductor is formed.
With the above screen printing method, there are a variety of dimensional dispersion factors to form the fine conductive patterns at high precision and stably, including (1) positional precision of screen, (2) positional precision of jig, (3) exudation of paste, (4) blurred printing, (5) degradation of screen, and (6) degradation of squeeze. Due to such an influence, the ultimate electrical characteristic (e.g., the inductance for a chip inductor, or the filter characteristic for a dielectric filter) may be affected. Consequently, it was obliged to make the trimming using a router which took a lot of steps with the filter to obtain good products.
In particular, in the case where there are irregularities or through holes such as an electrode on the end face of a chip element or a dielectric filter, it is not possible to solve the problems only by the screen printing of conductive paste. As a specific example, a dielectric filter having a fine conductor pattern formed on one side of the through hole in the dielectric block will be described below.
In the case where the pattern printing is made on the dielectric block of the dielectric filter as above constituted, a plurality of dielectric blocks are arranged on a jig at a time in consideration of the productivity, and then the screen printing is made using the conductive paste.
FIGS. 17A to 17E show a pattern printing process with the conventional screen printing. FIG. 17A shows a step of arranging the dielectric blocks 1 on a printing jig 2. The dielectric blocks 1 are arranged on the jig 2 having a plurality of cavities 3. FIG. 17B shows a cross section of the jig 2, in which the dielectric blocks 1 provided in the cavities 3 are arranged at a fixed spacing. FIG. 17C shows a step of printing a conductive paste 4, in which the conductive paste 4 is printed in a pattern 8 by a squeeze 6, using a printing screen 5 with a predetermined pattern.
However, the screen 5 has originally no distortion as shown in FIG. 17D, but the screen 5 may be distorted as shown in FIG. 17E by repeating this operation. The reason is that in the case where the dielectric blocks 1 are arranged on the jig 2 as shown in FIG. 17C, it is necessary to withstand a printing pressure only with the printing screen 5 at a portion of the spacing xcex94W on either side of the jig 2. Consequently, the printing screen 5 is loaded, and stretched, so that the positional precision is significantly worse.
On the contrary, since the screen printing is limited in respect of fineness, it has been examined in recent years that an electrode conductor of a predetermined pattern is produced through an exposure and development process (photo lithography process) using a photosensitive conductive paste (conductive paste having photo sensitivity).
In a production method employing such photosensitive conductive paste, the fine conductor pattern can be produced, but the following problems remain.
(1) Particularly, the screen printing has a drawback that a mesh mark produces a pinhole defect. Regarding this point, means for enhancing the flowability of photosensitive conductive paste was proposed in JP-A-10-112216.
(2) If a thick film is formed at a time, it takes not only considerable time to make exposure, but also the pattern precision is degraded. Therefore, it may be difficult to obtain a film thickness required for the electrode conductor of electronic component at a time. For example, in the case of an electrode conductor in the soldered portion, if the conductor is Ag, the amount (thickness) of conductor melting into the eutectic solder is 2.5 xcexcm at 250xc2x0 C., and 5 xcexcm at 280xc2x0 C. On the other hand, the photosensitive conductive paste is applied normally in a thickness of 10 to 20 xcexcm to make the treatment at high precision and an exposure time to increase the productivity. In this case, after sintering, the conductive paste has a thickness of about 5 to 10 xcexcm. Accordingly, with an Ag thickness of 5 xcexcm, the conductor Ag is exhausted at 280xc2x0 C. in one second.
(3) It is difficult to make exposure for the portion perpendicular to the light, particularly, the though hole with a large aspect ratio. It is difficult to form the through hole.
(4) The photosensitive conductive paste is often inferior to the non-sensitive conductive paste (conductive paste having no photosensitivity) available at present in the respects of conductivity or film thickness. Hence, it is difficult to obtain the photosensitive conductive paste having conductivity and film thickness comparable to those of the non-photosensitive conductive paste, or cheaper in the costs.
In this way, in the case where the electrode conductor is formed using the photosensitive conductive paste, there are a number of items that have not been solved yet.
It is an object of the present invention to provide an electronic component capable of not only enhancing the pattern printing precision which was the conventional problem, but also forming a pattern and an electrode in a predetermined film thickness suitable for the location where the electronic component is employed, and further forming the electrode in the portion with a high aspect ratio, and a method for manufacturing the electronic component.
Other objects and new features of the present invention will be more apparent when reading the following embodiments.
According to first aspect of the present invention, there is provided an electronic component comprising: a first electrode conductor section formed of the non-photosensitive conductive paste on a surface connected with a principal surface, an end portion at the principal surface side being made taper shape; and a second electrode conductor section having the photosensitive conductive paste exposed and developed on said principal surface; in that the end portion of the first electrode conductor section having a taper shape is overlapped at least a part of the second electrode conductor.
Preferably, the first electrode conductor section formed of said non-photosensitive conductive paste may constitute an end face electrode or a side face electrode on an end face or a side face of said component.
Preferably, the surface connecting with said principal surface may have a taper connection face, and the second electrode conductor formed by said photosensitive conductive extends from said principal plane to said taper connection face to overlap each other.
According to a second aspect of the present invention, there is provided an electronic component comprising: a first electrode conductor section formed of said non-photosensitive conductive paste on a principal surface; and a second electrode conductor having said photosensitive conductive paste exposed and developed, and being at least partly overlapped on said first electrode conductor, wherein contours of the overlapped areas of both first and second electrode conductor sections being coincident.
Preferably, the contours of the overlapped areas of both electrode conductor sections may be coincident and constitute the bumps.
According to third aspect of the invention, there is provided an electronic component comprising: a first electrode conductor section having said photosensitive conductive paste exposed and developed, by which an electrode area is defined; and a second electrode conductor section formed of a non-photosensitive conductive paste, which is formed in the electrode are a defined by said first electrode conductor section.
According to fourth aspect of the invention, there is provided an electronic component comprising: a dielectric block; a first electrode conductor section having a photosensitive conductive paste exposed and developed on a principal surface of said dielectric block; and an inner peripheral electrode conductor section formed of a non-photosensitive conductive paste on an inner peripheral face of a through hole that is opened through said principal surface, in that both electrode conductor sections are overlapped at least partly near an opening portion of said through hole on said principal plane to electrically conducts to make up a dielectric filter.
Preferably, according to the invention, the electrode conductor section formed of said photosensitive conductive paste and the electrode conductor section formed of said non-photosensitive conductive paste are at least partly overlapped with each other and sintered.
According to the fifth aspect of the invention, there is provided a method for manufacturing an electronic component comprising the steps of: forming a first electrode conductor section of a non-photosensitive conductive pattern on a surface connected with a principal surface, an end portion at the principal surface side being made taper shape the other plane; forming a second electrode conductor section having a photosensitive conductive paste exposed and developed on said principal surface; in that the end portion of the first electrode conductor section having a taper shape is overlapped at least a part of the second electrode conductor
Preferably, the surface connecting with said principal surface may have a taper connection face, and the second electrode conductor formed by said photosensitive conductive extends from said principal plane to said taper connection face to overlap each other.
According to the sixth aspect of the invention, there is provided a method for manufacturing the electronic component comprising the steps of: forming a first electrode conductor section of a non-photosensitive conductive pattern on a principal surface; forming a second electrode conductor section having a photosensitive conductive paste exposed and developed on said principal surface, the second electrode conductor section being at least partly overlapped on said first electrode conductor section; patterning said first electrode conductor section of the non-photosensitive conductive paste using said second electrode conductor section as a mask.